Polymerization processes using aliphatic maleimides

Abstract

Aliphatic maleimides and methods using the same are disclosed. Polymerization of compositions which include the compounds of the invention may be activated by irradiating the composition with radiation.

Description

FIELD OF THE INVENTIONThis invention relates generally to maleimide compounds and methods of using the same as photoinitiators in photoactivatable polymerization systems.BACKGROUND OF THE INVENTIONEthylenically unsaturated compounds, such as acrylate derivatives, can be polymerized by exposure to radiation, typically ultraviolet light, in the presence of a photoinitiating system. Typically, the photoinitiating system includes (1) a compound capable of initiating polymerization of the ethylenically unsaturated compound upon exposure to radiation (a “photoinitiator”) and optionally (2) a coinitiator or synergist, that is, a molecule which serves as a hydrogen atom donor. The coinitiators or synergists are typically alcohols, tertiary amines, amides, or ethers which have labile hydrogens attached to a carbon adjacent to a heteroatom.Numerous photoinitiators with varying structures are commercially available for use in different systems. However, nearly all commercially available radiat...

AI Technical Summary

Benefits of technology

The photopolymerizable compositions can be applied or deposited on a surface of a substrate using conventional techniques and apparatus. The composition can be applied as a substantially continuous film. Alternatively, the composition can be applied in a discontinuous pattern. The thickness of the deposited composition can vary, depending upon the desired thickness of the resultant cured product. One advantage of the invention is that relatively thick coatings of polymerizable compositions. For example, the inventors have found that PEG400DA comprising 2 to 10% by mole ECMI or 2AEMI can be effective for a 1.5 to 7 cm thick or bulk composition using a medium pressure mercury lamp (30 mW / cm).

is that relatively thick coatings of polymerizable compositions. For example, the inventors have found that PEG400DA comprising 2 to 10% by mole ECMI or 2AEMI can be effective for a 1.5 to 7 cm thick or bulk composition using a medium pressure mercury lamp (30 mW / cm).

Typically, the substrate is coated with the uncured photopolymerizable composition and passed under a commercially available UV or excimer lamp on a conveyer moving at predetermined speeds. The substrate to be coated can be, for example, metal, wood, mineral, glass, paper, plastic, fabric, ceramic, and the like.

The active energy beams used in accordance with the present invention may be visible light or ultraviolet light or may contain in their spectra both visible and ultraviolet light. The polymerization may be activated by irradiating the composition with ultraviolet light using any of the techniques known in the art for providing ultraviolet radiation, i.e., in the range of 200 nm and 450 nm ultraviolet radiation, and especially with the 308 nm emission from xenon chloride exciter lamps, commercially available from Fusion Systems, or by irradiating the composition with radiation outside of the ultraviolet spectrum. The radiation may be natural or artificial, monochromatic or polychromatic, incoherent or coherent and should be sufficiently intense to activate the photoinitiators of the invention and thus the polymerization. Conventional radiation sources include fluorescent lamps, excimer lamps, mercury, metal additive and arc lamps. Coherent light sources are the pulsed nitrogen, xenon, argon ion- and ionized neon lasers whose emissions fall within or overlap the ultraviolet or visible absorption bands of the compounds of the invention.

The compositions are useful in any of the types of applications known in the art for photopolymerizations, including as a binder for solids to yield a cured product in the nature of a paint, varnish, enamel, lacquer, stain or ink. The compositions can also be useful in the production of photopolymerizable surface coatings in printing processes, such as lithographic printing, screen printing, and the like. The compositions can also be useful in applications in which the compositions are applied to articles which are to be exposed to the environment, such as signage. Radiation cured coatings produced using conventional photoinitators typically degrade over time (as evidenced by yellowing, increasing brittleness, and the like), which degradation is exacerbated by direct exposure to sunlight. In contrast, radiation cured coatings prepared using the maleimide compounds can exhibit minimal degradation over time, even when exposed to direct sunlight. The maleimides can also be water soluble.

Problems solved by technology

However, nearly all commercially available radiation curing processes require an initiator incorporated into the formulation, a large percent of which is not consumed.

The presence of the residual photo-active compounds and extractables can result degradation of the physical properties of the article, such as decreased light fastness, discoloration, and lower resistance to oxidative degradation.

In addition, the residual photoinitiator can be extracted or leach out of the cured article or migrate to the surface of the article, which is undesirable in many applications.

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